26 down: short time in opposition? it was worthwhile
for which I have gleaned (very possibly wrongly!) 'tan_i'.
Although 'tanti', or indeed 'tansi', might fit the first part of the clue, as far as I know neither constitutes legitimate English!
6 down: energy put into mount of old, like highland crag?
for which I've 'ste_'. Obviously very tempting to put 'step', meaning mount or outcrop etc, but can only only come up with the following incredibly tenuous justification for doing so:
(mount) st. (michel etc...) e(nergy)...p(ut)
Help with either of these would be very welcome! :)